1. Field of the Invention
The present invention relates generally to hot tools to machine workpieces made of foam material and heat ablation apparatuses using the same and, more particularly, to a hot tool having enhanced machining accuracy and minimally discharging pollutants, and a heat ablation apparatus using the same.
2. Description of the Related Art
As well known to those skilled in the art, the manufacture of three-dimensional shapes from foam materials has been widely implemented in mold industries, test product manufacturing industries and design industries. Tools to machine workpieces made of foam material were proposed in U.S. Pat. No. 6,234,725, Korean Patent Application No. 2003-47255 and Korean Patent Application No. 2004-16967.
The tool of U.S. Pat. No. 6,234,725 is a type that cuts foam. Because this type of tool machines foam by cutting it, chips and dust are generated during a machining process. These chips and dust deteriorate working conditions. In consideration of this, in this US Patent, an air passage for the intake of chips and dust is formed in the tool. However, because the tool rotates at a high speed when cutting foam, few chips and little dust are actually drawn through the air passage.
To solve the above-mentioned disadvantages of U.S. Pat. No. 6,234,725, the inventor of the present invention proposed Korean Patent Application Nos. 2003-47255 and 2004-16967. Unlike U.S. Pat. No. 6,234,725, these patents shape foam by melting it, thus preventing chips and dust from being generated.
FIG. 1 shows a hot tool 10 disclosed in Korean Patent Application No. 2003-47255. As shown in FIG. 1, the hot tool 10 of No. 2003-47255 includes a heating wire 11. When voltage is applied to the hot tool 10, the heating wire 11 generates high heat of 700° C. or more and thus melts the surface of a workpiece, disposed adjacent to the heating wire 11, using radiant heat. Because this machining method can machine the workpiece without contact between the hot tool 10 and the workpiece, there is no cutting resistance caused by friction between the workpiece and the tool.
However, in this hot tool of No. 2003-47255, thermal energy is transferred to the workpiece through a medium, that is, the heating wire, having a very small surface area. Thus, the effective machining range, in which the workpiece is substantially pyrolyzed, is too narrow and, consequently, the time required to machine the workpiece is increased. Therefore, if this hot tool is used in a preliminary machining stage in which a relatively large surface area must be machined, only a small part of the workpiece is pyrolyzed, and most of the remaining part merely enters a molten state and may undesirably adhere to the workpiece or the hot tool, thus increasing surface roughness of the workpiece and the machining accuracy of the hot tool.
FIGS. 2A and 2B show a hot tool 20 disclosed in Korean Patent Application No. 2004-16967. FIG. 2A is a perspective view of the hot tool 20, and FIG. 2B is a sectional view of the hot tool 20. As shown in FIG. 2B, electrodes 26 and a heating wire 28, connected to the electrodes 26, are provided in the hot tool 20. The hot tool 20 includes machining parts 22 which protrude outwards from a circumferential outer surface of a shaft body of the hot tool 20, and receiving spaces 24 which receive molten polymer therein. Each machining part 22 protrudes in radial directions such that it contacts a workpiece. Each receiving space 24 has a concave shape such that molten polymer is easily received therein. Polymer melted by the machining parts 22 is received in the receiving spaces 24 and is heated in the receiving spaces 24 for a long time, thus being pyrolyzed. Therefore, in this patent, the time required to machine the workpiece is reduced, and the degree of melting of polymer is decreased, compared to the prior arts.
However, this patent has a disadvantage in that only when the hot tool moves in a longitudinal direction can molten polymer be removed during a machining process. Furthermore, because the hot tool must be heated to a high temperature to rapidly pyrolyze the polymer in the receiving spaces 24, it is very difficult to precisely machine the workpiece made of foam material.